George Clooney launched an investigation into a mystery caller who left him a voicemail urging him to ditch girlfriend, Sarah Larson.

The actor reveals in a new interview how he got his police-officer driver to track down the owner of a middle-age male voice, who warned: "Dude, your friends asked me to give you a message: Dump the bitch before you're sorry!"

According to Page Six, a reporter from New Yorker was present when Clooney played the message in front of Larson for the first time.

Not surprisingly, the former waitress didn't take to kindly to the caller's words of advice.

An outraged Larsen reportedly responded: '"Before you're sorry.' They say that I'm a stripper. There's a ton of stuff about that. I've never been a stripper.

"You know, just because I'm from Las Vegas, I must be a stripper. Because I'm a cocktail server, that means I'm an escort."

Clooney, insists he hasn’t fallen victim to a joke played by one of his showbiz pals.

"It's not a prank - none of my friends would do that," he insists.

However, Clooney's investigation hit a dead-end after tracing the  caller's number traced to a pre-paid cellphone.

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